It shall be the duty of the judge, when any convict is sentenced to imprisonment in the penitentiary, to commit the convict to the nearest jail which may be deemed safe, and by the next mail after the sentence to give notice to the warden of the penitentiary that such convict is confined, subject to his order, in a certain county jail, and to inform him whether, in his opinion, he is a dangerous criminal, and whether more than ordinary precautions will be necessary in guarding him.